<?php
/**
 * Created by PhpStorm.
 * User: Raymond
 * Date: 2021-06-25
 * Time: 10:29
 */
preg_match('/(a)(b)*(c)/', 'ac', $matches);
var_dump($matches);
preg_match('/(a)(b)*(c)/', 'ac', $matches, PREG_UNMATCHED_AS_NULL);
var_dump($matches);

$a = "a'bc";
echo $a;